Date:         Sat, 27 Jan 2001 20:23:20 -0500
Reply-To:     Gary Stearns <gstearns@OPTONLINE.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Gary Stearns <gstearns@OPTONLINE.NET>
Subject:      Re: '85 1.9L Stumbles Off Idle When Warm
Content-type: text/plain; charset=iso-8859-1

A suggestion with no guarantee of success: connect a digital voltmeter to
the output of the O2 sensor.  The output should fluctuate which is normal,
but if it's going much below .45 to .50 volts, she's running too lean.  Our
'88 had a massive idle stumble for several years (sounded like a race engine
with a wild cam that would barely run below 3,000 RPM) before I figured this
out. Tried everything that you have and more with no success 'til I found a
solution. Funny thing is it passed emission inspections well below standards
even while stumbling away.  If you find that the voltmeter says she's
running lean, maybe time to change the settings in the AFM.  The AFM wiper
can have it's static setting changed or it's spring tension changed. Sounds
like you will know where to look for these adjustments.   My suggestion is
to move the static setting slightly richer.  After using this, you may find
that you want to make the spring tension slighty tighter to keep it from
running too rich at greater throttle openings.  We eventually ran our engine
"open loop" with the O2 sensor connected to a voltmeter on the dash, but not
to the ecu.  Doing this taught me alot about digifant characteristics and
their effect on engine performance... **without having the O2 sensor trying
to undo what I was doing**.   Our manual trans Vanagon can now almost have
the clutch sidestepped from a stop without a stumble.  I don't know if what
I have done is an actual correction of the basic problem, or a band-aid that
helps the symptoms, but it has worked.

Gary
----- Original Message -----
From: "Chuck Mathis" <CMathis227@AOL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, January 27, 2001 9:39 AM
Subject: '85 1.9L Stumbles Off Idle When Warm


> This is making me nuts.
>
> When 'Roland' (Wolfsburg Westy, 1.9L Automatic, 57K miles) and I began our
> relationship almost two years ago he was showing signs of neglect -- not
bad
> but neglected.  Power output was pretty sad and he idled like a Harley.
> First shot was new cap, rotor and plugs -- solved a bunch of problems.
> Second round was a new Idle Stabilizer, Digitool (nothing to do with
running
> but I did upgrade from a Triumph-Adler ECU to a Bosch in the process),
Temp
> II sensor and throttle switch adjustment -- again a big improvement.  This
> fall I installed a new exhaust system (coated), muffler and O2 sensor --
> again big improvements.  When the van is cool the throttle response from a
> stop is outstanding but once the van is warmed to normal operating
> temperature it stumbles and backfires unless the full throttle position is
> engaged.  Even at full throttle it stumbles briefly before something
clicks
> (usually takes about half the width of an intersection) and it takes off.
> This only happens from a full stop.  Normal slowdown-speed up throttle
> response is very good.  Highway manners are excellent -- good power and
good
> mileage.
>
> Went through the Texas emissions test with flying colors.  Very low
numbers
> across the board.
>
> Last weekend I adjusted the idle speed and timing to Bentley specs.
>
> Last night I cleaned the AFM wiper strip and shifted the card ever so
> slightly.  The quality of the idle improved but once warmed up the stumble
> returned.
>
> What should I be looking at now?
>
> In case it matters, I have installed Bosch Platinium +4's, K&N
Filtercharger,
> Turbomax 14771 Muffler, and polished the throttle body throat.  The rotor
and
> cap have about 4K miles on them plugs have been in about 10K miles.  I've
> checked and tightened all the intake related hoses and fittings.
>
> Chuck
>